Historically, Uncle Tom was a [black] [man] born into slavery, who ended up sacrificing his own life to save the lives of other slaves. But, when this story was made into a movie, Uncle Tom was portrayed as a slave who gave his life for his master.
Now, an Uncle Tom is a [derogatory] term to describe a black man who acts white and talks white, or who is a [sell-out] to his own [race]. A black man who kisses white peoples asses, and who will turn his back on other black people to keep the approval of [whites]. A sell-out, an [ass kisser], a [race traitor]...
Ive also heard people describe an Uncle Tom as a [whitewashed] black man. A [black man] who may have been raised by [white people], and who therefore has the [manorisms] and [behaviors] of a [white man]. He would also speak like a dorky/nerdy white man.
A black man, who, while speaking to over the phone, one would think they were talking to a white man.